A major problem with current carbon dioxide absorber equipment is the difficulty (in some cases impossibility) experienced in achieving adequate heat autoclaving particularly if this is to be done after each patient use. Conventional equipment is fixed or semi-fixed and has not been designated to be easily dismantled and re-assembled with frequent straightforward autoclaving procedures in mind.
Conventional equipment typically includes a soda lime canister with separate valves. Such equipment need to be dismantled for autoclaving, and therefore is often not autoclaved between patients.
Additionally, many conventional canisters are bulky and heavy and therefore are usually only autoclaved on an infrequent basis. Also, some or all of the other components including metal and composite metal/plastic unidirectional and overflow valves (sometimes called adjustable pressure limiting (APL) valves), and fixed connecting parts bolted to the anaesthetic machine cannot be autoclaved without great difficulty and consequently autoclaving of these parts is rarely done.
Apart from the valves and absorber, the breathing circuit includes breathing hoses, a Y-piece or equivalent connector and a face mask, all of which should be readily autoclaved or replaced by single use equipment.
It is also known to provide single use absorbers or autoclavable plastic absorbers which can be removed or replaced as a single use device. However, the various associated equipment including unidirectional valves and/or an exhaust valve with or without a scavenging port are, in fact, separate pieces of equipment and do not form an integral part of the canister body.
An example of a known, single use carbon dioxide absorber device is the ISO-GARD CO.sub.2 ABSORBER SYSTEM manufactured by GIBECK-DRYDEN CORP. of Indianapolis, Ind. U.S.A. Although several known devices (including the GIBECK-DRYDEN device) most likely perform their intended function in a workmanlike manner, room for improvement exists. One area in which room for improvement exists is in the adjustability of known overflow valves. It is difficult to properly adjust the flow rate of gasses through the overflow valve in some known devices because it has been the Applicant's experience that the devices do not respond well to fine adjustments. This problem is especially acute at the low gas flow rates (e.g., 1or 2liters per minute) that are now being used more frequently.
The present invention has as one of its objectives the provision of a carbon dioxide absorber and integrated valve system for use with anaesthetic and resuscitation equipment which can easily be made portable, be easily dismantled from the equipment for sterilization and in some forms can be disposable for one off use.
Furthermore, it is an objective to provide an improved adjustable pressure limiting valve in such equipment for closely controlling the outflow of excessive gas in the circuit but yet automatically enables the breathing bag to be maintained in a normal inflated condition, particularly when used in patients breathing spontaneously.